This obscure company appears to have produced only two cameras - both TLRs and both in my collection here. Interestingly, neither the company nor its products appear in the two Kodak Museum-published histories of the Japanese camera, but they do feature briefly in McKeown, who dates the Marioflex to 1953 and the Osiroflex two years later. It looks like McKeown merely copied this information verbatim from Sugiyama, who shows a Marioflex version with a "Mario B" shutter, made by OMS Optical, and an Osiroflex credited to a name-changed "Osiro Optical Co".
For practical purposes, they pretty much qualify as the same camera.
Both cameras in Sugiyama have Rozeck lenses. Here's a complication. My Marioflex, with diamond-shaped OMS logo on the lid, has a lens labelled Osiro Kogaku Rozeck. The shutter is NKS-SC. So this is presumably a transitional model between the two in Sugiyama, but one is left to wonder what was the corporate history. A web search found nothing about this company, although an Oshiro Optical did operate in the fifties, making one or more 35mm cameras.
Any information gratefully received!
Taking lens is Osiro Optical 80mm f3.5
Shutter NKS-SC 1 to 1/200